Income Taxes - Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Effective tax rate, decrease from change in state tax rates, percent	1.90%
Derease on qualified production deductions, total, percent		6.00%
Decrease on qualified production deductions, current period, percent	2.30%
Decrease on qualified production deductions, prior period, percent	3.70%
Decrease on research tax credits, total, percent		3.40%
Decrease on research tax credits, current period, percent	0.50%
Decrease on research tax credits, prior period, percent	2.90%
Operating loss carryforwards	$ 10.7		$ 60.7
Unrecognized tax benefits	3.9	$ 3.4	3.9	$ 2.7
Unrecognized tax benefit changes in next 12 months	1.7
Unrecognized tax benefits, interest on income taxes accrued	1.0		4.9
Unrecognized tax benefits, income tax penalties accrued	0.1		$ 0.1
Change in accrued interest related to increase in unrecognized tax benefits and penalties	(3.9)
Valuation allowance, noncurrent	$ 1.1